Space reference device



July 6, 1954 c. A. WILEY SPACE REFERENCE DEVICE 3 Sheets-Sheet l Filed Aug. e, 1952 INERT/l RFRENCE S//VL MEMBER INVENTOR. Car/ V/ey A TT ORNE Y July 6, 1954 c. A. WILEY SPACE REFERENCE DEVICE 3 Sheets-Sheekl 2 Filed Aug. 8, 1952 ATTURNEY IN V EN TOR Carl A. W//ey DRW/N6 VOLT/165 /oo/. mia.

OUTPUT VOL TAGE July 6, 1954 c. A. WILEY 2,683,247

SPACE REFERENCE DEVICE Filed Aug. 8, 1952 3 Sheets-Sheet 3 S//VL TOPQI/E VULMGE FQ. 7 CRYSTAL "Gmo" Ur/L/zAr/o/v 1N VEN TOR. C dr/ H//Yey ATTORNEY Patented July 6, 1954 UNITED STATES PATENT DFFICE SPACE REFERENCE DEVICE Carl A. Wiley, Phoenix, Ariz., assignorto Goodyear Aircraft Corporation, Akron, Ohio, a corporation of Delaware Application August 8, 1952, Serial No. v303,447 11 Claims. (Cl. S18-489) This invention relates to apparatus for measand comprising an inertia member, torque senuring angular movement, and, more particuiarsitive means mounting the inertia member for ly, to an inertia member mounted in relation resilient vibrating movement about the axis, to an axis by torque sensitive means, With means means for changing at high frequency the radius for rapidly changing the radius of gyration of 5 of gyration of the inertia member with respect the inertia member-with respect to the axis, and to the axis, and means associated with the torque means associated with the torque sensitive sensitive means for indicating angular movemeans for indicating angular movement of the ment. apparatus. For a better understanding of the invention Prior to the present invention apparatus for 7L@ reference should be had to the .accompanying measuring angular velocity or movement has drawings wherein Figure l is a schematic illusbeen relatively heavy, space consuming, and extration of one apparatus employing the principensive, a typical apparatus in this field being ples of the invention. a gyroscope of mechanical-electrical type. Figure 2 is a schematic diagram of a modie Moreover, known apparatus is not only subject form of apparatus incorporating the principles to the objections noted, but often includes erof the invention; rors of progression. Figure 3-is an enlarged longitudinal vertical It is the general object of this invention to sectional View of the inertia member and the avoid and overcome objections to and diiiiculties torque sensitive members of the apparatus in oi known apparatus for measuring angular Figure 2; movement by the provision of apparatus char- Figure 4 is a transverse vertical sectional view acterized by light weight, relatively small space taken substantially on line IV-IV of Figure 3; requirements, inexpensiveness and simplicity Figure 5 is a schematic Wiring diagram of the coupled with high einciency and accuracy. phase discriminator of Figure l; and

Another object of the invention is the provision Figures 6 and 7 are diagrammatic showings of cf apparatus of the character described utilizing control mechanisms for adapting the apparatus the principle of rapidly changing the radius of to function in space reference capacity, or the gyration at al known frequency of an inertia like. member, measuring the change in torque charac- Having particular reference to Figure l of the teristics or the member resulting from any andrawings, the numeral I indicates an inertia gular movement of the apparatus, and correlatmember which may take any of a variety of ing the change torque with the radius of gyshapes or forms, but which conveniently is made ration changes to give an indication of angular in the shape of a disc and from piezo-electric movement of the apparatus. material, such as barium titanate. The inertia Another object of the invention is to provide member i is mounted axially of an axis A-A b piezo-electric means in apparatus such as demeans oi a torque sensitive element 2 which, Scribe@ likewise, may take a variety of shapes and which Another object of my invention is to provide can be made from a variety oi materials. In high frequency' apparatus oi the type described. the embodiment of the invention illustrated the Another object ci the invention is the provision 40 torque sensitive element 2 is in the shape of a of control mechanism for automatically re-posishaft of considerably less diameter than the intioning high frequency apparatus for sensing anertia member l, with the asis of the shaft coingular movement so that it will function in a ciding with the axis A-A. The torque sensitive space reference capacity. element 2 is iixed at one end to the inertia mem- Another object of the invention is to provide ber l, and another portion of the shaft, such as discriminating means for correlating high torque its opposite end, is xed against rotation, for exsignals with a high frequency reference signal ample, on a base 3. In one form of the invenfrom the means for changing the radius of gytion the torque sensitive element 2 is made from ration or the inertia member so as to provide an a piezo-electric material such as an ammoniindicaticn of angular movement of the apparaum dihydrogen phosphate crystal. tus. Some driver means are provided for rapidly The foregoing objects of the invention, and changing at high frequency the radius of gyraother objects which will become apparent as the tion and the moment of inertia of the inertia description proceeds, are achieved by apparatus member twith respect to the axis A-A, and de- Afor measuring angular velocity about an axis pendent upon the shape and the material of acces/i7 the inertia member i these means, indicated by the numeral d, can be piezo-electric, or the like. When the inertia member i is made from a piezo-electric crystal, such as barium titanate, the means i normally comprises a high frequency voltage source connected by electric leads 5 in driving relation to the inertia member by means of electro-conductive coatings 6 and l on opposite sides of the inertia member.

Electrode means, such as a pair of diametrically-opposed coatings or plates t and S are associate with the torque sensitive element 2 and are connected by electric leads le with an amplirler ii, the output of the amplifier passing to a phase discriminator i2. The discriminator likewise receives a reference signal by electric leads i3 from the driver means d, and the output of the phase discriminator l2 is connected to an angular movement indicator ill.

En the operation o the apparatus as described, it is evident that if there is any angular movement of the inertia member i about the axis AHA, then the cyclic and high frequency change of the radius of gyration of the inertia member and the attendant cyclic change in the moment or inertia of the member produces a cyclic torque about the axis A-A. The frequency of this torque is the frequency of the change in the radius of gyration, and the magnitude of the torque is proportional to the angular rate of rotation of the inertia member (usually caused by the turning of the entire apparatus) about the axis p -A. The inertia member i is caused to vib rate in rotation about the axis A-A inasmuch as the member i is relatively free to vibrate in this manner, the torque sensitive element 2 allowing it. This vibration is superimposed on the angular rotation about the axis A-A, this angular rotation having much lower frequency components whose measurement is desired. Oi course, the vibration of the inertia member i exerts a turning moment or cycling changes in turning moment on the torque sensitive element E, and this generates a torque signal from the electrodes and e to the amplier H which passes the amplified torque signal to the phase discriminator i2 which serves to synchronously demodulate the torque signal having reference to the cyclic reference signals passed to the discriminator l2 from the means d. The output of the phase discriminator i2 is indicated in the angular movement indicator irl, which as hereinafter described, can be used to indicate rate of angular movement, and by integration extent of angular movement, or which can be used to correct or compensate for angular movement to hold the apparatus against angular movement around axis A-A so that the apparatus becomes a space reference mechanism, like an attitude gyroscope. The device is designated in the drawings as a gyro in this sense.

rEhe embodiment of the invention illustrated in Figures 2, El and e includes the sensing element indicated as a whole by the numeral i5, and comprising an inertia member it and torque sensitive elements il and le mounting the inertia member i6. rEhe radius of gyration and the moment or" inertia of the inertia. nember it are cyclically varied by a driver i9 having electric leads 2i? xtending to a phase discriminator 2l in the iorm of a two phase induction motor, the leads 2E being connected to one of the two phases. The torque sensitive elements il and i8 are connected in electrical series with each other and to the primary of a transformer 22,

i the secondary of which is connected by electric lead 23 to the second phase ci the two phase induction motorV 2i. Amplification of the transformer output before passing to the motor 2i is usually advisable. When the inertia member i6 is a piezo-crystal the driver i9 takes the form of a relatively high frequency oscillator, such as a 1GO kilocycle oscillator. The output shaft of the induction motor 2l may be connected to a pointer 25, which can be spring to indicate rate of angular movement, or the output shaft of the induction motor can be coupled, as indicated by the dotted line 25, to the casing of the sensing mechanism i5 so as to move the casing about the axis i3-B to correct for or compensate for any angular movement thereof.

Figures 3 and 4i illustrate in greater detail the sensing mechanism i5, this mechanism including a cylindrical casing 26 which may be made airtight and from which the air may be evacuated if desired. As previously indicated, the inertia member i6 may be made from various materials capable of performing as herein described and may take a variety of forms, but it is conveniently made of a piezo-electrical crystal, for example, barium titanate, and the form or a disc or cylinder. 1n one embodiment of the invention the barium titanate crystal was made one centimeter thick in an axial direction and 2.56 centimeters in diameter. When using the barium titanate disc as the inertia member the driver it for rapidly changing the radius of gyration of the inertia member taires the form of a driving voltage created at a illu lrilocycle frequency and electrically connected to the inertia member i6.

Supporting the inertia member it from opposite sides are torque sensitive elements il and le which may be made in the :form oi hollow shafts as shown and from a piezo-electric crystal, such as ammonium dihydrogen phosphate. In the structure shown it is advisable to make the two torque sensitive elements il and it as two sections of the same ammonium dihydrogen phosphate cylinder in order to make the balance between these two elements as exact as possible. n the embodiment of the invention illustrated each torque sensitive element is .965 centimeter long, is one centimeter in diameter and is provided with a one-half centimeter axial hole. lThe torque sensitive elements il and i8 are adhesively secured to the inertia member it in alignment with the axis B-B thereof, and each torque sensitive element is supported from the casing 2E approximately half way of each elements length by three hollow rods spaced apart 12o degrees, the rods being indicated by the numeral 2l for torque sensitive element il and by the numeral 223 for torque sensitive element 28. Each torque sensitive element is provided with a pair of opposed electrodes 2@ and respectively, and these are connected by wires running through the tubes 2l and 2E to the primary of transformer 2li with one contact 2d and one contact 3c being connected to each other so that the elements are in series with the transformer.

By mounting the torque sensitive elements il and i?. at their torsional nodes in the manner described, the voltages set up from torsional oscil'iation are 180 degrees out of phase so that these torsional voltages alone are effective in energizing the transformer 22. Each of the crystais of the torque sensitive elements il' and i8 is capped and surrounded by a metal foil shield 3i and 32, respectively, which are grounded so that the output electrodes 29 and 3U are completely shielded from the driving electrodes to the inertia member i6.

lt will be understood that the output signal from the transformer 22 may be amplied and compared with the driving signal from driver I9 in a phase discriminate-r 'to obtain a D. C. signal proportional to rate of angular movement. However, since the output or torque signal is naturally in quadrature with the driving voltage the use of the two phase induction motor 2l is possible. The amplified output from the torque sensitive elements El and IS can be applied directly to one phase of the tivo phase induction motor 2l, the other phase of which is energized by the driver i9. It is evident that as the inertia member IS reverses its direction of rotation due to a change in its radius of gyration that the torque signal goes from leading to lagging the driving signal by 90 degrees and the motor 2i reverses its direction or" rotation. The motor torque is proportional to the signal from the torque element hence to the rate of rotation of the inertia member. The induction motor .5 must have its magnetic portions made or a metal oxide magnetic material, such as Ferroxcube, having permeability of over a thousand which has losses at the one hundred kilocycle operating irequency comparable to the losses in silicon steel at 60 cycles.

It will be understood that in the operation of the severai embodiments of the invention scribed 'that the high frequency change in the radius of gyration and the moment of inertia of inertia member I of Figure 1 and the inertia member it of Figure 2 results in no output in the torque sensitive elements supporting the inertia members as long as there is no rotation of the complete apparatus of Figure 1 about axis A-A or no rotation of the complete apparatus of Figure 2 about axis B-B- It is only when the appa ratus of Figure i turns about axis A-A or the apparatus of Figure 2 turns around axis B-B concurrently with the rapid change in the radius of gyration of the inertia member that the torque sensitive elements are energized to give an indication oi angular iovement, a measure of angular rate, or are used to compensate for any movement and to reposition the apparatus so that the torque sensitive element output remains zero to rotationally stabilize the apparatus in space.

The apparatus of the invention has been described solely in conjunction with a single axis, but it is readily evident that several of the apparatus of the invention can be combined to perform like functions in conjunction with two or more axes simultaneously, and that one particular application or" the apparatus of the invention is to provide an attitude indicating device similar to an attitude gyroscope.

In Figure 5 of the application is illustrated one typical phase discriminating circuit comprising a pair of diodes 33 and 34, couplings or trans-- formers i5 and 36, resistances 31, 38 and 39, and condensers lil and il connected in the manner illustrated. The purpose and function of the phase discriminator is as heretofore described.

Figure 6 more specifically illustrates a crystal angular rate measuring device utilization in which a crystal unit, such as I5, is driven or excited at high frequency by driver I9 which also supplies a reference voltage through a phase shifter 122 and amplier 43 to a phase discriminator I2. The output leads 23 of the crystal unit I5 supply a torque signal voltage through an amplifier 44 to the phase discriminator i2. The output of the phase discriminator is a D. C. voltage proportioned to the rate of angular movement and this is connected to a D. C. motor d5 which in turn is connected by mechanical linke age 46 to reposition the crystal gyro to its original position.

Figure 7 illustrates another crystal angular rate measuring device utilization in which the crystal gyro is again driven by a 1GO irc. exciter i9 which passes a reference signal to a 90 degree phase shifter il, through a mixer and lloc cycle lter 5, and an amplifier 7 to supply a 400 cycle reference voltage to a 400 cycle two phase motor 43. The torque signal voltage output of the crystal passes to a mixer and 400 cycle filter i9 and through an amplier 56 to supply a 40G cycle signal voltage to the second phase of motor d8, A 99.6 kc. oscillator 5i is provided to beat with the 1Go kc. inputs of mixers 45 and Si? to provide the 400 cycle outputs of the reference and torque signal to the motor 4S. Mechanical linkage 52 repositions the crystal i5 to provide the equivalent Of an attitude gyroscope.

From the foregoing it will be recognized that the various objects of the invention have been achieved by the provision of relatively inexpensive, light weight, small space consuming and yet highly efcient apparatus for measuring, indicating or compensating for angular movement. The principles of the invention have been particularly described in conjunction with piezoelectric crystals which comprise the preferred embodiments of the invention, but other electrical members or mechanisms capable of perm forming with substantially the high frequency characteristics described can be employed.

While certain representative embodiments and details have been shown for the purpose ot" illustrating the invention, it will be apparent to those skilled in this art that various changes and modications may be made therein without d' rting from the spirit or scope of the invention.

What is claimed l. Apparatus for measuring angular velocity about an axis and comprising a piezo-electric crystal forming an inertia member, torque seneitive means of the piezo-electric type mounting the inertia member for resilient vibrating Inovement about the axis, high frequency means for rapidly changing the radius of gyration of the inertia member with respect to the axis, a phase discriminator, means supplying a reference signal to the discriminator from the means for changing the radius of gyration of the inertia member, means connecting a torque signal from the torque sensitive means to the discriminar-or, means for shifting the phase of one of the nais, and angular movement indicating means connected to the output of the discriminator.

2. Apparatus for measuring angular velocity about an axis and comprising a piezo-electric crystal forming an inertia member, torque sen tive means of the piezo-electric type mounting the inertia member for resilient vibrating movement about the aXis, high frequency means for rapidly changing the radius of errati-cn of the inertia member ui;h respect to the axis, 'tivo phase induction motor, a transformer, the torque sensitive means producing electric signals out of phase with eaech other and connected to the transformer, the output of the transformer conf nected toone phase of the induction motor, the

7 other phase of the induction motor being ccnnected to a reference signal from the means changing the radius of gyration of the inertia member, and angular movement indicating means driven by the motor.

3. Apparatus for measuring angular velocity about an axis and comprising a piezo-electric crystal forming an inertia member, a high irequency oscillator connected to the crystal for rapidly changing the radius of gyration thereof, piezo-electric crystal means mounting the crystal of the inertia member so that the crystal means are stressed mechanically by the cha-nge in the radius of gyration if there is any rotation about the axis by the apparatus, electric leads to the crystal means, and means connected to the electric leads and the oscillator and responsive to angular' movement of the apparatus about the axis.

4. Apparatus for about an axis and comprising a piezo-electric crystal associated with an inertia member, a high frequency oscillator connected to the crystal for rapidly changing the radius of gyration thereof, piezo-electric crystal means mounting the crystal ci the inertia member so that the crystal means are stressed mechanically by the change in the radius of gyration if there is any rotation about the axis by the apparatus, electric leads to the crystal means, and phase discriminator means connected to the electric leads and the oscillator and responsive to angular movement of the apparatus about the axis.

5. Apparatus 'for measuring angular velocity about an axis and comprising a barium titanate crystal forming an inertia member, a high frequency oscillator connected to the crystal for rapidly changing the radius of gyration thereof, ammonium dihydrcgen phosphate crystal means mounting the crystal or the inertia member so that the crystal means are stressed mechanically by the change in the radius of gyration if there is any rotation about the axis by the apparatus, electric leads to the crystal means, and means connected to the electric leads and the oscillatorl and responsive to angular movement of the apparatus about the axis.

c. Apparatus for measuringl angular velocity about an axis and comprising a barium titanate crystal forming a disc shaped inertia membery.'

a high frequency oscillator connected to the crystal for rapidly changing the radius of gyration thereof, ammonium dihydrogen phosphate crystal means in the form of a shaft mounting the crystal of the the shaft being fixed axially to the center of the disc iorming the inertia member, and another portion oi shaft remote irom the disc being fixed against rotation so that the crystal means are stressed mechanically by the change in the radius of gyration if there is any rotation about the axis by the apparatus, electric leads to the crystal means, and means connected to the electric leads and the oscillator and responsive to angular movement of the apparatus about the axis.

'7. Apparatus for measuring angular velocity about an axis and comprising a piezo-electric crystal forming a shaped inertia member, a frequency oscillator connected to the crystal for rapidly changing the radius of gyration thereof, piezo-electric crystal means in the form of a shaft mounting the crystal of the inertia member one end of the shaft being l'ixed axially to the center of the disc forming the inertia measuring angular velocity inertia member one end ofl member, and another portion or the shaft remote from the disc being fixed against rotation so that the crystal means are stressed mechanically by the change in the radius of gyration if there is any rotation about the axis by the apparatus, electric leads to the crystal means, and means connected to the electric leads and the oscillator and responsive to angular movement of the apparatus about the axis.

8. Space reference apparatus comprising a pieno-electric crystal forming a disc shaped inertia member, a high frequency oscillator connected to the crystal for rapidly changing the radius of gyration thereof, piezo-electrical crystal means in the form of a shaft mounting the crystal of the inertia member one end of the shaft being xed axially to the center of the disc forming the inertia member, and another portion of the shaft remote from the disc being xed against rotation so that the crystal means are stressed mechanically by the change in the radius of gyration ii there is any rotation about the axis by the apparatus, electric leads to the crystal means, and a two phase induction motor having one phase connected to the electric leads and the second phase connected to the oscillator and responsive to angular movement of the apparatus about the axis.

9. Space reference apparatus comprising a piezo-electric crystal forming an inertia member, torque sensitive means of the piezo-electric type mounting the inertia member for resilient vibrating movement about an axis, high frequency means for changing the radius of gyration of the inertia member with respect to the axis, a high frequency oscillator having a 'frequency just slightly under the frequency of the high 'frequency means, mixer and filter means for beating the frequencies of the oscillator and the high frequency means against each other and having an output of a fevv hundred cycles, a second mixer and iilter means for beating the frequencies of the oscillator and the output of the torque sensitive means against each other and having an output oi a few hundred cycles, a two phase direct current motor having one phase connected to the rst mixer and lter means and a second phase connected to the second mixer and filter means, and mechanical linkage connecting the motor to the inertia member and torque sensitive means to angularly reposition them.

l0. Apparatus for measuring angular velocity about an axis and comprising a piezo-electric crystal forming an inertia member, torque sensitive means of the piezo-electric type mounting the inertia member for resilient vibrating movement about the axis, high frequency means for rapidly changing the radius ci gyration of the inertia member with respect to the axis, a phase discriminator, means supplying a reference signal to the discriminator from the means for changing the radius of syration of the inertia member, means connecting a torque signal from the torque sensitive means to the discriminator, a direct current motor driven by the output of the discriminator, and mechanical linkage connecting the motor and the inertia member and torque sensitive means to reposition the member and means to their original angular position.

il. Apparatus for measuring angular velocity about an axis and comprising a piezo-electric crystal forming an inertia member, torque sensitive means of the piezo-electric type mounting the inertia member for resilient vibrating movement about the axis, high frequency means for rapidly changing the radius of gyration of the inertia member with respect to the axis, a phase dscriminator, means supplying a reference signal to the discriminator from the means for changing the radius of gyration of the inertia member, means connecting a torque signal from the torque sensitive means to the discriminator, and angular movement indicating means connected to the output of the discriminator.

References Cited in the file of this patent Number UNITED STATES PATENTS Name Date Lyman July 4, 1950 Peterson Dec. 5, 1950 Johnson Mar. 27, 1951 Morrow Nov. 4, 1952 Lyman Feb. 3, 1953 

